The present invention relates to a position securing system for restraining an occupant in a land vehicle or aeronautical vehicle in the seated and standing positions and during shift between the seated and standing positions.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
Land vehicles or aircrafts, in particular those used for rescue and transport of injured people, like ambulances or rescue helicopters, require an occupant in certain situations to carry out various activities in seated position as well as standing position, whereby in either position, the occupant should be secured for his or her own safety as well as in the interest of the injured. The same is true during a switch from seated to standing position, or vice versa, so as to prevent endangering the occupant, e.g. when a land vehicle abruptly slows down or an aircraft makes a sudden change in flight direction. Harnesses used for all these situations should hereby not only restrain the occupant but also allow the occupant to carry out the intended activity.
Harnesses typically include a two-part lap belt, two leg loops, a rear belt, two shoulder belts, a back belt, and a belly-side center buckle. Retractors, called “Emergency Locking Retractors” (ELR), are used for the lap belts and shoulder belts to lock the belts, when the vehicle or occupant slows or stops abruptly. The combination of harness and retractors for a position securing system is generally referred to in the concerned art as “High Mobility Restraint” (HMR). Conventional retractors have a sensor mechanism to recognize an acceleration of the belts, when encountering a sudden movement of the vehicle and to ultimately lock so as to prevent a further unwinding of the belts. As a result of this sequence of steps, the so-called “film spool effect” is caused by which the helically wound belts are inadvertently lengthened and no longer rest snugly about the occupant. As a result, the occupant is exposed essentially unprotected to sudden decelerations and accelerations. This is especially true for the lap belts which are especially subject to intense loads in view of the mass distribution of a human body during abrupt movement of a vehicle and resultant significant deceleration or acceleration. Such high loads cause the belts to lengthen, resulting in unacceptable shift of the pelvis area of the occupant.
The use of a so-called “Automatic Locking retractor” (ALR) is also known which lock to maintain a fixed belt length during use but are unsuitable for a High Mobility Restraint because the retractor has to be released, when the occupant is seated. This is unacceptable for safety reasons.
Retractors are generally constructed to spirally wind-up and store the belts. In view of the limited pull-back force of volute springs provided in the retractors and the inherent stiffness of the belts as well as their non-compact structure and surface, the belts cannot be wound in the retractors in an optimum way. A taut winding from layer to layer can be realized only, when the axis of the winding drum is locked and a pull force is applied on the belt. As a result, not only does the diameter of the wound belt decline but also the overall length of the stored belt. As a result, a longer belt strap is released from the retractor.
In aeronautical vehicles, the use of an emergency locking retractor, which reacts in response to a pull-out of a belt from the retractor, is prohibited at least in connection with lap belts because rough flight movements could cause an occupant's body to shift relative to the seat, without exceeding response values of such an emergency locking retractor. Thus, a secure restraint of the occupant in the seat cannot be assured.
It would therefore be desirable and advantageous to provide an improved position securing system to obviate prior art shortcomings and to allow an occupant to carry out all required movements in seated and standing positions as well as during shift between the seated and standing positions, while still reliably restrain the occupant to meet stringent demands.